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Effect of High Temperature on Fruit Productivity and Seed-Set of Sweet Pepper (Capsicum annuum L.) in the Field Condition


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Chili peppers grow best and are likely to reach the maximum yield at temperature ranging from 21 °C to 33 °C. In the plastic house, the temperature increases to 42 °C in the summer. The fruit set and fruit growth were effected correlative with the high temperature condition. In this study, Shishito peppers were grown in plastic house in two periods (in the early stage of April and the end stage of May) in 2012. The difference in temperature between two periods of planting was about 4 °C. In fruit set period of the 2nd planting, the weather condition is disadvantage for fruit growth. During temperature changed in the summer, the fruit weight and the number of seeds per fruit of both “Shishi-homare” and "105c-10" varieties were reduced about 0.5 and 2.8 times in the 2nd planting when compared with the 1st planting. The number of seeds per fruit reduced corresponding with the fruit size under the high temperature condition.
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Journal of Agricultural Science and Technology A and B
& Hue University Journal of Science 5 (2015) 515-520
doi: 10.17265/2161-6256/2015.12.010
Effect of High Temperature on Fruit Productivity and
Seed-Set of Sweet Pepper (Capsicum annuum L.) in the
Field Condition
Tran Loc Thuy1 and Murakami Kenji2
1. Department of Plant Protection, Cuu Long Delta Rice Research Institute, Can Tho 900000, Vietnam
2. Department of Bioproduction Science, Ishikawa Prefectural University, Ishikawa 921-8836, Japan
Abstract: Chili peppers grow best and are likely to reach the maximum yield at temperature ranging from 21 °C to 33 °C. In the
plastic house, the temperature increases to 42 °C in the summer. The fruit set and fruit growth were effected correlative with the high
temperature condition. In this study, Shishito peppers were grown in plastic house in two periods (in the early stage of April and the
end stage of May) in 2012. The difference in temperature between two periods of planting was about 4 °C. In fruit set period of the
2nd planting, the weather condition is disadvantage for fruit growth. During temperature changed in the summer, the fruit weight and
the number of seeds per fruit of both “Shishi-homare” and 105c-10 varieties were reduced about 0.5 and 2.8 times in the 2nd planting
when compared with the 1st planting. The number of seeds per fruit reduced corresponding with the fruit size under the high
temperature condition.
Key words: High temperature, seed-set, fruit productivity.
1. Introduction
The origin of pepper (Capsicum annuum L.) is
Mexico and the neighboring areas of Central
America. Shishito is one of four popular sweet
pepper cultivars (Hushimi-ama type, Shishito type,
Bell type and F1 type) in Japan [1]. Fruit is small,
green and non-pungency. In Japan, The crop of sweet
pepper begins in the last stage of spring and harvests
from May to November [2]. During this time, the
temperature increased strongly, when the extreme
temperature of more than 40 °C sometimes was
recorded in August [3]. Under plastic house in the
field, the inside temperature will be higher.
Temperature strongly influenced the development of
fruit and flowers of chili pepper [4]. The optimum
temperature for chilli pepper cultivation is 21-33 °C.
Low and high temperature condition affect the size
of fruit and seed germination ability [5, 6]. Under
Corresponding author: Tran Loc Thuy, Ph.D. student,
research field: plant production.
changing of weather, temperatures are higher than
the optimum chili’s growing, thus the plants are
objected to disadvantageous temperature period [7,
In general, high temperature influences many
aspects of plant physiology and growth, which may
lead to significant losses in crop productivity in
many species due to limited vegetative, reproductive
growth and seed yield [9]. According the survey of
Erickson and Markhart [10], fruit set and
productivity of pepper reduced during periods of
high temperature. High temperature frequently
occurs after anthesis of chilli pepper and strongly
impacts the reproduction and yield. However, the
rare investigation about the effect of high
temperature on chili pepper crop has been elucidated.
Therefore, the present study aimed to study the
impact of high temperature during summer period in
Japan on the phenological and morphological
character of fruits of Shishito pepper.
Effect of High Temperature on Fruit Productivity and Seed-Set of Sweet Pepper
(Capsicum annuum L.) in the Field Condition
2. Materials and Methods
The experiment was carried out in plastic house of
Okayama University, Japan. Four varieties derived
from Shishito (Capsicum annuum L.), viz.,
“Shishi-homare” (a favorite variety in Japan),
“105c-10” (low-pungent mutation line derived from
“Shishi-hormare”), “Kounou Shishito” and “Kairyo
Shishito” were used in the current experiment.
The seeds were sown in sowing tray in both the
planting times. The 1st time was on April 9, 2012 to
August 16, 2012, “Shishi-homare” and “105c-10” were
planted in this time; and the 2nd time was on May 30,
2012 to October 30, 2012, four varieties were planted
and filled with commercial soil (300 mg/L N, 450 mg/L
P and 370 mg/L K). During the 1st planting, the pots
containing the seeds were kept in the growth chamber,
which set at a daily 16/8 h (light/dark) with a
temperature of 28/20 °C, respectively. After three weeks
when seedlings were at 3-4 leaf stage, 30 seedlings of
each variety were transplanted to plastic pot (10.5 cm,
containing commercial soil) and kept in the plastic
house, and distance between two pots is 15 cm. At
anthesis stage, 10 plants of each one were transplanted
again to the ground in plastic house. The distance
between two plants was 50 cm and the distance
between two rows was 1.2 m. The seedlings were
trained with two main branches. Depending on the daily
temperature, plants were watered once or twice per day.
The plants were supplied with fertilizer of NPK fertilize
(20 g/m2), and Ca and Mg (80 g/m2 each), respectively.
Temperature in plastic house was recorded with
thermocouples connected to data-logger. The plant
growth situation before the 2nd transplanting was
recorded. All the individual flowers were labeled for
finding the days after flowering (DAF). Fruits from
flowers of 28-30 DAF were harvested with one fruit
per branch weekly. The morphological characteristic
of harvest fruits (fruit size, fruit diameter, fruit length)
and number of seeds were recorded. Fruits from
labeled flowers were harvested once per week from
the last of June to the middle of August for the 1st
planting and from middle of August to the end of
October for the 2nd planting. The data obtained were
analyzed following Tukey-test (P 0.05).
3. Results and Discussion
The temperature in plastic house increased
gradually from April 15th, and the highest temperature
of 42 °C was recorded from the early August to the
early September (Fig. 1). During the 1st planting
period (Fig. 1a), the temperature averaged from 28 °C
to 33.4 °C in day and 11.8 °C to 21.4 °C at night,
which gradually increased and reached a peak of
42 °C in the early August. The temperature increased
nearly 4 °C from the 1st planting to the 2nd planting.
The 1st flower in the 2nd planting appeared in the
late July, when the maximum temperature is about
41.6/24.6 °C (day/night) (Fig. 1b). The difference in
temperature between the 1st planting (the early stage
of June) and the 2nd planting for the 1st flower
opening was 7 °C.
No significant difference was observed between
“Shishi-homare” and “105c-10” in the number of days
to the 1st flowering. When the temperature increased,
the days to the 1st flower reduced, respectively (Table
1). Similar results were reported by Qumer et al. [11].
No significant difference was observed in the node
number in all the varieties during both planting times.
This might be because all the varieties belong to
Shishito group, and thereby exert similar
morphological characteristics.
The fruit size of harvested fruits, such as fruit
length, fruit weight, fruit diameter and seed number
per fruit were recorded in Table 2 and no difference
was observed in the fruit weight, fruit length, fruit
diameter and seed number per fruit between
“Shishi-homare” and “105c-10” in the 1st planting.
But when the temperature increased in the 2nd
planting, the morphological characteristic of fruits in
all varieties changed, fruit weight and number of seeds
per fruit of both “Shishi-homare” and “105c-10” were
reduced about 0.5 times and 2.8 times, respectively.
Effect of High Temperature on Fruit Productivity and Seed-Set of Sweet Pepper
(Capsicum annuum L.) in the Field Condition
(a) (b)
Fig. 1 The temperature condition during culture of two times planting.
E: the early stage of month (1st-10th), M: the middle stage of month (11th-20th), L: the last stage of month (21st-30th).
Table 1 The number of days to the 1st flowering, the node number of the 1st flower and the plant height in the 2nd
Plant time Variety Days to the 1st
The node number of
the 1st flower
The height in the 2nd
transplanting (cm)
1st planting Shishi-homare 57.8 ± 0.9a 15.1 ± 0.7
15.4 ± 0.8c
105c-10 56.6 ± 0.7a 14.3 ± 0.6
15.9 ± 0.62c
2nd planting
Shishi-homare 53.4 ± 1.7
15.0 ± 0.8
17.0 ± 1.0c
105c-10 52.3 ± 1.1
15.1 ± 0.7
18.0 ± 0.7
Kounou Shishito 53.2 ± 0.8
16.9 ± 1.0a 21.8 ± 1.1a
Kairyo-Shishito 52.6 ± 1.3
15.1 ± 1.0
19.0 ± 1.1
a-cDifferent letters within the same column indicate a significant difference at 5% level by Tukey’s test.
Table 2 The morphological characteristics of harvested fruits at 28-30 DAA.
Plant time Variety Fruit weight (g) Fruit diameter (cm) Fruit length (cm) Numbers of seed/fruit
1st planting Shishi-homare 8.9 ± 5.1
1.6 ± 0.4
6.8 ± 2.2
51.8 ± 33.1
105c-10 8.9 ± 4.9
1.7 ± 0.3
6.8 ± 2.1
54.1 ± 34.9
2nd planting
Shishi-homare 4.3 ± 1.6a 1.2 ± 0.2a 5.0 ± 1.1ab 18.3 ± 23.58a
105c-10 4.5 ± 1.2a 1.3 ± 0.2a 5.2 ± 1.5ab 19.9 ± 18.9a
KounouShishito 3.9 ± 1.6a 1.3 ± 0.3a 4.6 ± 1.3a 25.3 ± 25.1a
KairyoShishito 4.4 ± 2.1a 1.3 ± 0.3a 4.9 ± 1.9ab 27.0 ± 22.3a
a and bDifferent letters within the same column indicate a significant difference at 5% level by Tukey’s test.
The chili peppers grow best and are likely to reach
the maximum yields at temperature from 21 °C to
33 °C [3]. After the 1st flowering in the 2nd planting,
the temperature increases fluctuating from 37 °C to
42 °C, and thereby affects the fruit weight. The fruit
diameter and fruit length in the 2nd planting were
smaller than these in the 1st planting. Among the
varieties, fruits of “Kounou Shishito” are the smallest
in shape. In 1982, Ali and Kelly [12] reported that
fruit weigh, fruit length and fruit diameter of sweet
pepper reduced in the high temperature conditions. In
Shishito pepper, fruit weight reduced significantly and
seeds per fruit was lowered under high temperature
(38/30 °C day/night) [13].
The morphological characteristics of fruit were
strongly affected under high temperature (Fig. 2). The
highest fruit weight and fruit length were recorded on
July 8 in harvested “Shishi-homare” fruits of the 1st
Effect of High Temperature on Fruit Productivity and Seed-Set of Sweet Pepper
(Capsicum annuum L.) in the Field Condition
planting (Fig. 2a). In both “Shishi-homare” and
“105c-10” varieties in the 1st planting, fruit weight,
fruit diameter and fruit length reduced rapidly after
July 22, 2012, which correlates with the increase
temperature at this time. The fruit weight reduced
strongly responding to high temperature in both
“Shishi-homare” and “105c-10” varieties.
In the 2nd planting, the 1st flower appeared when
the temperature stayed in high condition (37.8/24 °C,
day/night), after that the temperature increased rapidly
(a) (b)
(c) (d)
(e) (f)
Fig. 2 The change of morphological fruit under two temperature regimes of two times of planting.
Effect of High Temperature on Fruit Productivity and Seed-Set of Sweet Pepper
(Capsicum annuum L.) in the Field Condition
and remained a long time. It correlates with the
development of four morphological fruit varieties
when the fruit weight, fruit diameter and fruit length
were small in the 1st harvested time and decreased
gradually. After September 14th, fruit weight, fruit
diameter and fruit length begun to increase, but it was
still smaller than that in the 1st planting. The
“Kounou Shishito” variety had the smallest fruit
weight and fruit length (Fig. 2d and 2f) in almost
harvested time.
During the 1st flower appearing in the 2nd planting,
the temperature condition fluctuated in 33-42 °C, thus
the weight of fruit was effected. When the weight of
fruit decreases, the diameter and the length of fruit
will reduce, correlatively. The diameter and the length
fruit in the 2nd planting were smaller than that in the
1st planting. Thus, all of Shishito varieties in this
experiment were impacted by high temperature.
In Japan, the annual temperature has been
increasing at rate of 1.1 °C per century since 1898. As
temperatures rise, the numbers of days with the
minimum temperatures 25 °C and the maximum
temperatures 35 °C are increasing, respectively [14].
In plastic house, the temperature is higher than outside.
High temperature (35 °C) has kept in long time
since the early of June. The highest temperature in
plastic house was 42.05 °C, which was recorded by
thermocouples. Shishito pepper grew best under the
field and green house with temperature ranging from
21 °C to 33 °C [3, 13]. Field and controlled
environment observations of pepper production
indicate substantial abortion of floral buds occurs
when day temperatures are 34 °C and/or night
temperature are 21 °C. Thus, when the maximum
temperature per day was 34 °C during the
day and night temperature 21 °C in early stage of
July (Fig. 1a), the fruit weight, fruit diameter, fruit
length and number seed of fruit decreased rapidly until
the lst harvest of the 1st planting and the almost
harvest time of 2nd planting. Fruit developed under
over the suitable condition, therefore harvested fruits
from the 2nd planting were smaller than that from the
1st planting (Fig. 2 and Table 2). Exposure to high
temperature, from microspore mother cell meiosis of
pepper flower to tetrad dissolution, in greatly reduces
pollen viability and anther dehiscence [15]. High
temperature inhibits the development of pollen grains
during the period of final tetrad formation to tetrad
dissolution. The reduction of pollen viability
effectively reduces fruit size and fruit set [10]. After
fertilization, the fruit size was determined by cell
divisions and cell expansions. The Shishito pepper
fruit width was the most sensitive to high temperature
until 10 DAF and less effected from 30 DAF
onwards [13]. Exposure to high temperature
throughout fruit development significantly reduced
Shishito pepper fruit weight. The reduction of fruit
length and fruit diameter responds the reduction of
fruit size in the high temperature condition in the 2nd
planting stage.
The reduction of seed numbers per fruit may have
been partly responsible for the reduction of fruit size.
A positive correlation was observed between fruit
weight and number of seeds per fruit of sweet pepper
[10, 16]. In the 2nd planting, under the high
temperature condition when the fruit weight
decreased, the seeds/fruit reduces in the same way.
Besides, under high temperature condition, the
reduction in the number of viable pollen affect
fertilization capacity, hence reducing number of
seeds per fruits. After fertilization, abortion of seeds
during the initial stages is probably due to failure in
proper cell division, which might due to high
temperature [13]. Thus, numbers of seed in all
varieties reduced strongly in the 2nd planting
compared to the 1st planting.
The results indicated that a significant response of
Shishito pepper was observed under high temperature
condition in the summer. Fruit quality of Shishito was
reduced drastically. Thus, managing the time to
sowing and harvesting is necessary for growing chilli
Effect of High Temperature on Fruit Productivity and Seed-Set of Sweet Pepper
(Capsicum annuum L.) in the Field Condition
4. Conclusions
The morphological fruits (the fruit weight, the fruit
diameter, the fruit length and number of seeds per fruit)
under high temperature decreased strongly. The
results indicated a significant difference in the
response of Shishito when the temperature increased
in the summer. Fruit quality of Shishito reduced
clearly in bad condition for growing. Thus, managing
the time to sowing and harvesting is so necessary
when growing sweet pepper.
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West Java Province in Indonesia has a geothermal district, one of the existing power plants is Wayang Windu. Besides the geological factors, the development of geothermal energy is determined by socio-economic. This paper examines the preliminary study of direct geothermal energy utilization in a tea plantation in Malabar, Indonesia. The land that has not been cultivated yet is available in that area, and it is near the Wayang Windu. The greenhouse design for 1 hectare which divided into six bays using a cascade cycle from Wayang Windu power plant. This study select capsicum annuum as a case study regarding the opportunity to produce in Bandung City. The minimum heat supply for the greenhouse is 1.25 MW from the hot wastewater from Wayang Windu. The estimation of the greenhouse will reduce carbon emission by around 84% compare with industrial diesel oil (IDO).
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Background: Drought is also one of the most widespread abiotic stresses that adversely effects the growth and development of plants. To investigate the effect of salicylic acid and drought stress on several physiological and chemical reactions in sweet pepper plants, the experiment was achieved as a factorial based on a completely randomized design in greenhouse. Drought stress levels were non-stress conditions (irrigation with field capacity), moderate stress (30% field capacity irrigation) and intense water stress (60% field capacity irrigation) and three concentrations of salicylic acid included 0 (as control), 0.5 and 1 mM were sprayed on the plant in three to four leaf stages. Results: The results showed that drought decreased fresh and dry weight of shoots and roots, leaf relative water content (RWC), fruit diameter and length, the index including chlorophyll and leaf area and increased electrical conductivity (EC), antioxidant activity, total phenolic content, ascorbate, polyphenol oxidase (PPO) and ascorbate peroxidase (APX) activity. After application of foliar salicylic acid, all of the above parameters, except the electrical conductivity content, increased. Conclusions: From the results of this experiment it is concluded that salicylic acid provides a better tolerance for drought stress in pepper plant through its influence on vegetative, biochemical and physiological characteristics.
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Global temperature rise is emerging as an alarming threat to agriculture and especially for vegetables, as they are more sensitive to high temperature because of their succulent nature. Vegetables include different edible plant parts such as leaves, stems, stalks, roots, tubers, bulbs, flowers, fruits, and seeds. An increase in temperature impairs the growth and development of vegetable plants and eventually reduces their yield. Heat tolerance is a complex quantitative trait that involves a series of physiological, biochemical, and molecular pathways. This complexity is further exacerbated by the presence of a large magnitude of genotype × environment and epistatic interactions, so breeders have to face challenges during development and selection of heat tolerant genotypes. Understanding the response of plants and resistance mechanisms involved in heat tolerance would help the breeders in formulating strategies to improve vegetable productivity under heat stress. In this review, firstly the impact of heat stress on the morphological, physiological, and molecular processes of different vegetables have been described, then discussed adaptation mechanisms employed by plants to combat heat stress. Finally, conventional and potential genomic strategies i.e. marker-assisted breeding, quantitative trait loci mapping, genome wide association, genomic selection, genetic engineering, and genome editing that are being used by the breeders to create heat resistance are presented. For vegetables, genome editing, and transgenic approaches need to be combined with conventional and marker-assisted breeding activities to develop heat tolerant varieties as these efforts will lead to tangible practical outcomes that will improve the vegetable productivity.
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A study was conducted to determine the response of several varieties of large chilli (Capsicum annuum L.) to Trichoderma enrichment on planting media and Boron fertilizer applications. The study was conducted from June to September 2017 at the Experimental Garden of the Faculty of Agriculture, Hasanuddin University, Makassar in the form of factorial Split Plot Design with 2 factors. Experiments were set with large chili varieties as the main plot consisting of var. Karina, var. Tombak, and var. Panex 100 F1, while the combination of Trichoderma enrichment and Boron fertilizer was set as subplots consist of 6 treatment combinations. The results show that there was a significant interaction between the treatment of varieties and Trichoderma-Boron on plant height parameter and there was a significant effect of the varieties treatment on the number of productive branches and the number of fruits per plant. In addition, significant effect of the Trichoderma-Boron treatment was shown in the parameters of fruit length per plant 100 HST. The interaction that gave the best results was in the treatment of Trichoderma asperellum 4 g plant-1 and Panex 100 F1 varieties on plant height of 47.77 cm. The treatment of varieties that gave the best results was Karina variety and the combination treatment of Trichoderma-Boron that gave the best results was the treatment of Trichoderma asperellum 4 g plant-1 + Boron 1 mg L-1.
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The morphology, marketable yield, main flowering and fruiting parameters, and the capsaicinoid content in different parts of mature green and red fruits of seven local hot pepper (Capsicum annuum L.) populations has been studied. Morphological characters and productivity values were estimated by agronomic analysis. Capsaicinoid content was determined by HPLC. Plants from these populations showed uniform development and uniform height ranging from 53-58 cm. Based on the ability to flower and on fruit setting, local pepper populations could be divided into two homogenous groups having an average of 120-160 flowers/plant. Cultivars 'Chaabani' and 'Baklouti Kairouan' produced an important marketable yield (863 and 752 g/plant, respectively). Total capsaicinoid content varied according to the population, and within the same population according to the stage of maturity and different parts of the fruit. Capsaicinoid content was higher in green pepper fruits than in red ones, higher in the placental part than in other parts, but lowest in seeds as well as in green and red fruit. 'Piment Sesseb', 'M'sarreh' and 'Rouge Long' populations had the highest total capsaicinoid contents in green and red pepper fruit and are recommended for pepper fruit production in season crops destined for the fresh market and as a spice (pepper powder).
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High temperature reduces fruit set in bell pepper [Capsicum annuum L. var. annuum (Grossum Group)], and reduction of pepper productivity, resulting from high temperature, may be a direct effect of temperature or an indirect effect of water stress induced by increased vapor pressure deficits (VPDs) at high temperature. We evaluated responses of plant growth, reproduction, net photosynthesis (PN), chlorophyll fluorescence, predawn respiration, leaf water potential, and stomatal conductance of 'Ace' and 'Bell Boy' bell pepper to elevated temperature (33°C) with increased VPD (2.1 kPa) or elevated temperature with no increase in VPD (1.1 kPa). VPD had no effect on flower number or fruit set and did not adversely influence the physiological processes measured. Therefore, deleterious effects of high temperature on pepper fruit set does not appear to be temperature induced water stress, but is more likely a direct temperature response. Elevated temperature decreased fruit set but not flower production. Gas exchange measurements suggest failure to set fruit was not due to reduced leaf photosynthesis.
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A study on heat tolerance in sweet pepper was conducted at the Asian Vegetable Research and Development Centre (AVRDC), Taiwan from December 1999 to May 2000. Experiments were carried out to investigate the influence of 29/23°C and 24/18°C stress on 12 sweet pepper genotypes on growth, development, reproductive behaviour and yield potentialities and to verify the results of the phytotron study. Performance of 12 sweet pepper genotypes was evaluated under two different temperature regimes of 24/18° C and 29/23° C in the phytotron. Plant height was found higher at 29/23° C compared to 24/18° C. High temperature reduced percent fruit set as well as size of fruits. Individual fruit weight was higher (7.44-125.00 g) when grown at 24/18°C and lower (5.35-103.80 g) at 29/23°C. Out of 12 genotypes, SP00l, SP002, SP004, and SP012 performed poor in respect of per plant yield at higher temperature compared to the lower temperature. So, these four genotypes were considered to be heat sensitive than the others. Leaf proline content of the sensitive genotypes decreased under the high temperature conditions and the heat tolerant lines produced higher amount of proline indicating the role of proline in expressing the heat tolerant capability of sweet pepper genotypes concerned.
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Since the beginning of civilization, the man has developed technologies to increase the efficiency of food production. The use of plastic mulch in commercial vegetable production is one of these traditional techniques that have been used for centuries. Studies were conducted to assess the efficacy of plastic mulch on growth and yield of two hot pepper hybrids, viz. Sky Red and Maha in poly/plastic tunnel. The treatments were black plastic mulch, clear plastic mulch and bare soil as control. Both hot pepper hybrids mulched with black plastic showed significantly better vegetative growth (plant height, leaf area etc) and fruit yield. Clear plastic mulch significantly increased soil temperature and reduced the number of days to first flower than black plastic mulch and bare soil. However, fruit yield was higher by 39.56 and 36.49% respectively in both hybrids when they were grown on black and clear plastic mulch as compared to bare soil. Overall results indicated that the use of plastic mulch is an ideal option to maximize hot pepper productivity as well as to extend their production season in poly/plastic tunnels.
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The aim of this work was to investigate whether parthenocarpic fruit growth could avoid flushing, i.e. an irregular yield pattern, in sweet pepper. Plants were grown in a greenhouse compartment from April until August. Half of the plants were grown without a fruit set treatment (control), whereas parthenocarpic fruits were allowed to develop on the other plants by preventing self-pollination and applying auxin to the stigma. For node positions 3 to 17, fruit set per node varied between 21 and 55% for control plants [coefficient of variation (CV) = 11%], whereas auxin-treated plants showed much less variation in fruit set (41–57%; CV = 5%) and average fruit set was higher. In agreement with fruit set, fruit yield was also much more regular in the auxin-treated plants. Fruit fresh yield varied between 0.2 and 1.0 kg m−2for control plants (CV = 20%), and between 0.4 and 0.8 kg m−2for auxin-treated plants (CV = 9%). Results showed that developing seeds in sweet pepper fruits are the main cause of the abortion of new flowers, and irregular fruit set and yield. Parthenocarpic fruit growth resulted in flatter, 30% smaller fruits, because of a reduction in fruit growth rate; the duration of fruit growth was 1 week longer than for fruits from control plants. Parthenocarpic fruits were hardly affected by blossom-end rot (BER) with only 1% of fruits being affected compared to 31% in the control. Total dry mass production was the same for treated and control plants; however, in auxin-treated plants, 50% of the total dry mass was allocated to the fruits, compared to 58% in control plants.
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High temperatures adversely affect crop productivity of several plant species including bell pepper (Capsicum annuum L. var. annuum). The objectives of this study were: (1) to determine whether flower ontogeny is adversely affected by high temperature during different phases of development, including pre- and post-pollination events; (2) to determine the duration of high temperature exposure necessary to cause reduction in fruit set; and (3) to determine whether injury to the pistil or stamen during development is responsible for reduced fruit set during high temperature. We determined that flower buds at <2·5 mm in length, corresponding to microspore mother cell meiosis to tetrad dissolution, and flowers that reached anthesis during the high temperature exposure had reduced fruit set when exposed to 33 °C for 48 or 120 h. Flower buds at <2·5 mm in length also had reduced pollen viability when exposed to 33 °C for 120 h. Morphological examination demonstrated that meiocytes initiated tetrad formation, but after dissolution the microspores remained small and clumped without a thick exine. High temperature exposure at a late-development, pre-anthesis stage did not affect pistil or stamen viability, but high post-pollination temperatures inhibited fruit set, suggesting that fertilization is sensitive to high temperature stress.
In order to evaluate the advantages of parthenocarpy in the breeding of Capsicum, we investigated the percentage of fruit set after emasculation or excision of styles, fruit size, and amounts of β-carotene, capsaicinoids, and ascorbic acids of the seedless fruits of Capsicum annuum L. 'Shishiroh' no. 562. Seedless fruits were induced from ≈80% of flower buds after emasculation or excision of styles. The levels of β-carotene (44.07 μg·g -1), capsaicin (1.73 mg·g -1), and dihydrocapsaicin (1.12 mg·g -1) of mature seedless fruits were 10 times higher than those of seeded fruits. The amount of ascorbic acid, however, was at the same level (≈230 mg/100 g). The length of the seedless fruit was ≈50% smaller than that of the seeded fruit at 2 weeks after the flowering and decreased to 44% at mature stage.
An analysis was performed on chili pepper [Capsicum annuum (L .) cv. Huay Si Thon and Shishito] seed vigor and quality produced by plants grown under control and high temperature conditions (29 • } 2/24 • }2 and 36 + 2/27 • } 2 • Ž, mean day and night temperatures, respectively) after anthesis to elucidate the effect of high temperature during seed development on seed quality. High temperature significantly reduced fruit growth in both varieties . More than 20 % of the seeds produced under the high temperature regime were flat with a dark brown color and did not germinate. High temperature inhibited seed fresh and dry weight increase and the seed size was slightly reduced. Standard germination of Huay Si Thon and Shishito seeds occurring under the high temperature conditions was lower than that of the control seeds by 28 and 25 %, respectively. Similarly, seed vigor was reduced, as evidenced by the reduction in the accelerated aging germination rate and the higher value of the germination index. Protein content was maximal during the early stages of seed development and decreased afterwards continuously during the seed maturation stage, while no conspicuous reduction of the protein content by heat was observed. High temperature reduced the carbohydrate content of seeds by 40 % in Huay Si Ton and 50 % in Shishito, respectively. High temperature reduced the lipid content to less than half. These results suggested that high temperature during seed development reduced chili pepper seed germination and vigor, presumably due to the limitation in the accumulation of storage products, especially carbohydrates, and lipids.
A plot experiment was carried out to determine the plant growth and mineral composition of three Solanaceous fruit vegetables for the responses to diurnal temperature alternations. Eggplant, sweet pepper, and tomato were grown in four phytotrons with diurnal temperature fluctuations between day and night temperatures (DIF) set constantly 12 hours day and night of 15/25°C, 17.5/22.5°C, 20/20°C, 25/15°C, and in a plastic-house as a control with average air temperature of 31.3°C at day-time and 19.1°C at night-time. After six weeks of cultivation, the growth of three tested crops as reflected in leaf dry weight, plant height, stem dry weight and root dry weight were significantly reduced by a negative DIF of 15/25°C compared to other DIF treatments and the control. In contrast to the growth parameters, a positive effect was observed on the average mineral absorption in all three crops. A negative DIF of 15/25°C increased Ca, K, and Mg content in the fruit, root, and stem of eggplant and tomato. The results suggest that all DIFs may be beneficial to greenhouse or field grown Solanaceous vegetable producers, by controlling the vegetative growth which will facilitate the crop management, with no limitations on uptake rates of mineral nutrients which are required to determine yield and fruit quality.
The effects of pre-anthesis temperature on the size and shape components of fruits from three bell and two pointed-fruit type cultivars of sweet pepper were investigated in growth chambers, glasshouses and the field. Three temperature regimes of constant 18°C (low), 25°C/18°C, day/night (intermediate) and constant 35°C (high) were applied to plants at the third leaf stage through the third branching node formation. Thereafter, plants were allowed to grow either in a glasshouse maintained at 25°C/18°C, day/night temperature or in the open field until harvest. Large, medium and small fruits were obtained at the intermediate, high and low pre-anthesis temperatures, respectively. A high temperature increased the mean number of locule per fruit (shape component), in the five cultivars as compared with intermediate temperature. In the bell types, the number of four-loculed (tetralocular) fruits significantly increased, while that of three-loculed (trilocular) fruits decreased. A low temperature also resulted in a minor increase in the mean number of locules as a result of a slight increase in the number of tetralocular fruits; yet most fruits were unmarketable because they were short and blunt. The increase in the number of locules per fruit was associated with improvement in the blockiness of the bell type fruits, but not the pointed type fruits. Medium size blocky fruits, which meet the high market standards, were obtained at high pre-anthesis and intermediate post-anthesis temperatures.